Reduce memory consumption by setting the generate-debug-attributes
option to false. This option is set in
the lib/configuration.properties file.
This will disable debug attribute generation (used to trace DITA-OT
error messages back to source files) and will reduce memory consumption.

Set dita.preprocess.reloadstylesheet Ant property
to true. This will allow the XSLT processor
to release memory when converting multiple files.

Run the transformation again.

java.io.IOException: Can't store Document

After running a JavaHelp transformation, you may receive a java.io.IOException:
Can't store Document message.

This problem occurs
when HTML files unrelated to the current transformation are found
in the output directory. Delete the content of the output
directory and run the transformation again.